A classmate has a beautiful "Taibai Zui" Helan stone handicraft, as shown in figure 1. In order to measure the density of this Helan stone, he conducted the following experiments.

(1) According to the illustrated spring dynamometer, the scale value is 0.2N, the index is 1.4N, and the gravity of Helan stone is g =1.4n.,

∫g = mg, ∴ mass of Helan stone: m = gg =1.4n10n/kg = 0.14kg =140g.

(2) According to the measuring cylinder shown in the figure, measure the volume of water, that is, the volume of Helan stone V=50ml=50cm3,

The density of Helan stone ρ = mv =140g50cm3 = 2.8g/cm3 = 2.8×103kg/m3.

(3) hanging Helan stone under a spring dynamometer and measuring its gravity G,

When Helan stone sinks into the water, read the pointer f of the spring scale, and the buoyancy of Helan stone is F = G-F,

∫F float =ρwater gV row，

∴ The volume of Helan stone V=V row =F floating ρ water g=G? Fρ water g

So the answer is: (1)140; (2)50; 2.8× 103; (3) The specific method of measuring the volume of this Helan stone is as mentioned above.